The invention relates generally to wind turbine rotor control systems, and more particularly, to automatic blade pitch control systems for wind turbines employed as electrical generators connected to the electrical grid.
Blade angle or pitch can be controlled to regulate output torque. The '646 patent discloses an all-mechanical system in which blade loading or blade moment automatically controls rotor pitch via a rotary control linkage having a spring biasing mechanism connected to the carriage. The blade load provides the forcing function to the control mechanism in an inherent closed loop whose transfer function in effect can be tailored by cam design, for example, to maximize output power over a design range of wind speeds. Passive, all-mechanical systems are particularly desirable because they are inherently fast reacting and reliable due to their relative invulnerability to environmental factors.
The linkage design of the '646 patent is particularly suitable for wind turbines for remote power applications with little or no servicing. However, the design is not optimal for wind farm applications involving larger routinely serviced machines.